The following abbreviations are defined as follows:
RS Relay Station
BS Base Station
MS Mobile Station
SS Subscriber Station
AP Access Point
CDMA Code Division Multiple Access
LU Location Update
PG Paging Group
PC Paging Controller
NE Network Entity
DCD Downlink Channel Descriptor
DL Downlink (BS towards MS via RS)
UL Uplink (MS towards BS via RS)
As wireless technology has advanced, a variety of wireless networks have been installed, such as cellular and other wireless networks. Some wireless networks are based upon the Institute of Electrical and Electronics Engineers (IEEE) 802.11 family of Wireless LAN (WLAN) industry specifications. Other wireless technologies are being developed, such as IEEE 802.16, also referred to as WiMax, industry specifications. IEEE 802.16 defines the wireless air interface specification for wireless metropolitan area networks. A number of working groups are engaged in efforts to improve on this technology.
In WiMAX or in general other cellular-type wireless systems, the MS belongs to one PAGING_GROUP area. Similarly the BS also belongs to one (or more) PAGING_GROUP(s). A PAGING_GROUP ID that identifies a particular PAGING_GROUP is transmitted on a broadcast channel (in WiMAX, it is transmitted on a DCD and/or MOB_PAG_ADV message). The MS monitors these messages (MOB_PAG_ADV message is transmitted according to MS PAGING_CYCLE and PAGING OFFSET). When the MS moves from one PAGING_GROUP area to another PAGING_GROUP area, it initiates a location update procedure. As per the current specification of IEEE802.16 (IEEE802.16-2004 and IEEE802.16e-2005), the location update procedure is performed between the MS and the BS. Similarly, when the RS moves from one PG to another PG it will initiate a location update procedure.
A wireless relay network is a multi-hop system in which end nodes (e.g., MS/SSs) are connected to the BS or AP via a RS. All traffic between the end nodes and the BS/AP passes through, and is processed by, the RS. One non-limiting example of a relay network is currently under discussion for 802.16 Mobile Multi-hop Relay (MMR), which is a task group 802.16j. The MMR work focuses on defining a network system that uses RSs to extend the network coverage and/or to enhance the system throughput.
As may be appreciated, if the RS is itself mobile, such as by being installed on a mobile platform such as a vehicle (a terrestrial vehicle, a water-based vehicle, or an airborne vehicle), the mobility of the RS with respect to the BS and the MS (or SS) adds an additional level of system complexity. In practice, a given RS may have numerous MSs attached to it at any given time. If the RS moves out of one location area (defined by a Paging Group) to another location area (defined by another Paging Group), this event will trigger location update signaling for all of the idle state MSs attached to the mobile RS. This event would thus abruptly increase the signaling message load and increase overall congestion in the system since all idle state MSs will essentially simultaneously perform the location update procedure, which involves a bidirectional signaling message flow, via the RS, between the BS and the affected idle state MSs.